MFR Metal Film Resistors Welwyn / TT Electronics MFR Metal Film Resistors are professional grade approved to BSCECC 40101-803 and 019 and offer tolerances down to 0.5%. Welwyn / TT Electronics MFR Metal Film Resistors feature a 1Ω to 1MΩ resistance range along with a 0.4W to 0.75W power rating. The series offers 200V or 350V rated voltage and operates over a -55°C to +155°C operating temperature range.